Age-resisting rubber compound and process of making same



, Patented May 10, 1927.

UNITED STATES PATENT OFFICE.

ERNEST R. ERIDGWATER, OF WILMINGTON, DELAWARE, AND DONALD HOWARD IOWERS, OF PENNS GROVE, NEW JERSEY, ASSIGNORS TO E. I. DU PONT DE NE- MOUBS 8c COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELA- WARE.

AGE-RESISTING RUBBER COMPOUND AND PROCESS OF MAKING SAME.

Ho Drawing. Application filed July 3,

This invention relates to the art of inhibiting the deterioration of or in part from vulcanized rubber by the in- V corporation of certain agents having the property of retarding the deterioration or aging of the rubber. More particularly the invention involves the coating of the'particles of such pr'eservingagent with a finely divided substance or dust before their incor- JO poration with the rubber.

The deterioration of rubber goods on aging is thought to be largely due to oxidation of the rubber or the rubber compound. Many organic compounds which have the property of retarding the oxidation and improving the aging properties of rubber are well known to those familiar withthe art of rubber compounding and manufacture. Among them may be mentioned aromatic diamino 2 compounds such as meta-phenylene diamine and benzidine, aromatic dihydroxy compounds such as hydroquinone and aromatic hydroxy-amino compounds such as paraaminophenol. None of these substancesis widely used because they have in common several disadvantageous properties, the principal one being that it is very dificult to uniformly disperse them in rubber compounds. Even when they are finely ground there appears to be a tendency for the particles to coalesce. This is exhibited during storage as well as while the material is being incorporated with the rubber. The primary object of our invention is to disperse such anti-oxidants uniformly throughout the rubber.

Another object is to obtain a maximum and uniform preservin effect from a given quantity of an anti oxi ant.

A final object is to avoid the spotting which commonly resultstrorn an uneven distribution of the anti-oxidant.

We have discovered that if the finely divided anti-oxidizing a ents are intimately mixed with a more fine y divided substance or dustprior to their incorporation in the rubber compound that uniform dispersion of the anti-oxidizing agents throughout the rubber is reatly facilitated. The particles .50 of the fine lhis coating of fine particles over the somegoods made wholly ydivided substance coat or cover the particles of the anti-oxidizing agent...

1926. Serial No. 120,516.

what larger particles of the anti-oxidant compound completely prevents the larger particles from adhering or coalescing during storage or during the operations of mixing, calendering and tubing the unvulcanized rubber or during or after vulcanization.

A variety of methods of obtaining an intimate mixture of anti-oxidizing agent, and inert substance may be employed. For example, the anti-aging compound may be precipitated in a suspension of the dust. 111 a preferred embodiment of our process they anti-agingagent is ground in the presence of 'the dust or powder. By this method, in addition to effecting a thorough coating of the particles of the agent, the presence of the finely divided dispersing substance makes it possible to grind the anti-oxidant compound more finely than would be otherwise possible, because, in the absence of such substances during the grinding operation, many of the small particles which are produced by breaking up large particles of the anti-aging compound coalesce to again form large particles before they pass out of the grinder. When the finely divided dry inert substance is present, the small particles are probably coated by soon as they are formed and the inert substance prevents them from coalescing.

- Any mill which is suitable for finely grinding organic or inorganic materials may be used for carrying out the invention. The mineral matter may, for example, be precipitated barium sulfate, zinc oxide, finely divided clay, calcium carbonate, silica, or any other fine dry powder. The antioxidant material may be any of those meny organic or inorganic compound which has the property of tioned above or anv other retarding the oxidation or improving the aging properties of rubber. We have successfuily practiced this invention using a varietyot combinations. For example, we have employed para-aminophenol ground with an equal weight of precipitated barium sulfate; para-aminophenol ground with an equal weight of zinc oxide, and meta-phenylenediamine ground with an equal weight of precipitated barium sulfate. In each of these cases the grinding was done one large scale with full sized plant equipment.

the mineral substance as iii to illustrate the upplicution i. rentiou;

' Ingrcdientu. Forte. Smoked sheets (l ii ule crepeuflmnflw u hit it ilinc onide (5 volumes) 3d. 915 tlurhon block 15 volumes) no Eiulifur M i5 Diphenylguunidine U. to .dn intimote mixture of equul purto oft precipituted lieriuln sulinte poru-oniindphenol d it. hit 'ilotul to in the ohove ernnnple the ingredient-e Were incorporuted with the rubber in u type 0t miner commonly employed in the urt. it is obvious that the percentoges ot" the 'rnrioue ingredients or theproportion oi finely divided dry powder to the orgunic nntioridont compound may he yoried within Wide limit: without depui'ting.-trom the spirit ot this invention. Any compound may he used which improves the aging properties of ruhbcr end uny finely divided muteriol which is adopted to covering the porticles of the unti-onidzrnt compound and preventing their coalescence. lLilrerviee norturol, synthetic or recioimed ruhher, or ruhher substitutes no gutter, percho, moy he employed. We, theretore ish it to he distinctly understood thot the invention is not limited to the moteriols, proportions and methods of mining descrihed oho've. I

Upon yulconinution o. unitormly colored unspotted product is ohtuinednhich product shows encellent resistance to We ch:

1. The process ot preserving 'o. cured rulober composition which process comprises incorporating with soid composition, prior to curing, on timute mixture oitln timely divided owder and o. suhstonce'odopted to retard the uginqg of the ruhher.

2. The method of uniformly impregnating e moss comprising" ruhher With n, finely dirided enti-uging compound, the portieles ot which tend to odhere, which method comprises the step of efiecting on intimote min tore oi eoid compound w th or dust udopted to cont the porticlcs thereoit.

3. The method olt uniitormly dietrihuting on anti-oping compound throughout more trrree.

.hher, "nhicl method. comprises reducing" the unti-uging corn-- to of line suhdivieion in the r dry doirst ud upted to cont the odueinp; unitorinly ed, until-d 5 ier composition Which rises eliectin intimate mixture or u .;y divided anti-urging compound and a. dry dust edu'pted to cent the particles oit suid compound, incorporutinpg" the dust couted compound. with the ruhhcr and u yulczinirn inp; ogrent und yulennininp;

5. .the method set forth in cluiin t Wherein the anti-aging compound is on uroinotic umino compound udupted to retard the oridution 0t ruhher.

ti. 'lhe i'oethod set torth in cluim d in the until-aging compound compound he ring; one or Wli6178- is on orornutlc more hydroiry groups end one or more uinino groups in the nucleon.

l. the method not torth in clonn d 111 the untinpging compound 1e Whereurn-omino- (iii phenol and the dust comprises oriunu sol photo.

8. A uniformly colored ruhher composition luring distributed throughout its mass or finely divided untingine" compound, the particles of euid compound heing coated With on inert dust. I 1

9. fin ontioging ruhher composition termed lay incorporeting' with the rubber prior to its ulczrninotion, on intimate mixture oi u. pulverulent dry dust end a. finely diyided snhstnnce udopted to retard the oging ot the ruhher.

to. do enti oging rubber composition hovinp; unitormly incorporated throughout its moss e finely divided aromatic amino coon pound odopted to retard the oxidation or the ruhher, soid compound having been, prior to its incorporotiou intimately admixed with o. duet odupted to coat the particles thereof. it; do onti-oging rubber composition having uniformly incorporated throughout its muse linely divided para-omino-phenol, said.

compound honing been, prior to its incororotion intimately admixed with or dust of horium eultute; In testimony n. nnewnrnn. norm u. none.

whereof We 'ottin our sigma-V tld till 

